The Stonehenge Memorial is a full-sized replica of its original namesake in England, except this one is built of concrete, is not in ruins, and sits on a hill overlooking the Columbia River Gorge with a view of Mount Hood (on a clear day). It was commissioned by a local businessman in 1918 as a memorial to three men killed in World War I.
If you go:
Wear walking shoes and check the weather, as this is an outside venue. Bring camera and binoculars. Open during daylight hours. Admission is free, but donations are welcomed. Summer or fall are best, but it is open year round.
Links:

Stonehenge Drive
Goldendale, Washington 98620 USA